This invention relates to electronically conductive polymers, and more particularly to composite articles or polymer blends containing electronically conductive polymers.
It is known to prepare coated articles by electrostatic painting methods. In such methods, a paint or coating is charged or ionized and sprayed on a grounded article, and the electrostatic attraction between the paint or coating and a grounded, conductive article results in a more efficient painting process with less wasted paint material, and thicker and more consistent paint coverage, particularly when the article has a complex shape. When articles fabricated from metals are painted, the metal, which is inherently conductive, is easily grounded and efficiently painted. In recent years, there has been an emphasis on the use of polymeric materials in the manufacture of articles, particularly in applications requiring reductions in weight and improved corrosion resistance, such as automotive applications. However, polymers typically used in such processes are insufficiently conductive to efficiently obtain a satisfactory paint thickness and coverage when the article is electrostatically painted.
One method that has been used to prepare electrostatically coated polymers is to employ compositions containing conductive fibers, such as described in European Patent Application No. 363,103. However, adding such large amounts of fibrous fillers to a polymer can adversely affect both the polymer's physical properties and paint finish. U.S. Pat. No. 5,188,783 discloses a method for making electrostatically coated articles from composites containing ion-conductive polymers. However, such articles may be less conductive than desirable for use in electrostatic coating processes.
PCT Publication No. WO 94/07612 discloses a process for preparing electrostatically paintable polyurethane compositions by the incorporation of ion-conductive metal salts. However, the conductivity of such compositions may be less than desirable for certain electrostatic painting processes.